US2107255A

US2107255A - Method of treating carbonates

Info

Publication number: US2107255A
Application number: US742624A
Authority: US
Inventors: Mccomb Parker
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-09-04
Filing date: 1934-09-04
Publication date: 1938-02-01
Anticipated expiration: 1955-02-01

Description

Feb. 1, 1938. P. MccoMB METHOD OF TREATING CARBONATES Filed Sept. 4, 1934 Parker M 60/77 5,

Patented Feb. 1, 1938 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to the reduction of minerals and ores to oxides and by-product gases.

It is an object of my invention to provide a roasting oven which will roast stone or ores without permitting the stone, at any place in its travel through the oven, to come into direct contact with the products of combustion.

A further object of this invention is to provide a roasting oven with a vertical type roasting chamber in which the material being roasted may be lowered as a unit.

Another object of this invention is the provision of a roasting oven having a hopper located in the path of the products of combustion whereby to dry the charge.

Another object of this invention is to provide an improved process of burning stone, ore or the like, and to separate the resulting by-product gases by allowing them to stratify according to their various specific gravities.

Other objects and advantages of my invention will be apparent during the course of the following description.

In the accompanying drawing forming a part of this application, and in which like numerals are employed to designate like parts throughout the same,

Fig. l is an elevation view in part section of a roasting oven embodying my invention,

Fig. 2 is a cross sectional view of the same on line 22 of Fig. 1,

Fig. 3 is a cross sectional view of the same on line 33 of Fig. 1,

Fig. 4 is a cross sectional view of the same on line 4-4 of Fig. 1,

Fig. 5 is a cross sectional view on line 5-5 of Fig. 1, showing details of a valve feature of this invention.

In the drawing wherein, for the purposes of illustration, is shown a preferred embodiment of this invention, numeral I designates the foundation of the same. The foundation is fabricated from structural steel or other suitable building materials and is designed to hold up the oven to a suificient height to permit dump carts or other type conveyors to be passed under the oven to receive the finished product. The outer wall, forming the stack 2 of this oven, is constructed of fire brick throughout its entire length. However, other types of material may be substituted for fire brick toward the top of this oven where the heat is less intense. From the foundation l, upwardly to line :1:a:, the stack 2 of this oven is made in the form of a hollow rectangular prism. From line :c-r upward to the top of the stack, it is formed in the shape of a hollow cylinder.

Located inside the stack 2, there is a roasting chamber 3, which is uniformly rectangular in cross sections throughout its entire length. This chamber is anchored along its narrow faces to the stack 2 from points 4 down to the bottom of the stack 2. From the bottom of the stack 2 to points 4, gas spaces are provided between the wide faces of the roasting chamber 3, and stack 2. To prevent any distortion of the roasting chamber which might result from the condition of high combustion temperatures, it has been found advisable to anchor the roasting chamber 3 along its narrow faces to the stack 2. From points l, upwardly, with the exception of the area at the discharge manifolds 5, the roasting chamber 3 is spaced from the stack 2 on its narrow faces as well as its wide faces to permit products of combustion to contact a greater heating surface.

The roasting chamber 3 is to be constructed out of suitable refractory materials having a high thermal conductivity value, such as aluminum oxide, beryllium oxide, thorium oxide, silicon carbide, zircon, or from metals such as tungsten, molybdenum, etc., having high melting points. The roasting oven is preferably constructed by superimposing individual tiles, one on another, and cementing them together.

Numeral 5 designates discharge manifolds. These manifolds are fabricated from the same materials that the roasting chamber 3 is fabricated. These manifolds 5 may be cast as units but are more preferably constructed in some superimposed hollow tile construction followed in the construction of the roasting chamber 3. Exhaust ports 5 are provided in the narrow walls of the roasting chamber 3. These ports are slanted upwardly so that they can not get clogged with stone.

Numeral l designates discharge pipes through which the generated gases may be drawn off by means of a pump not shown.

Numeral l0 designates a funnel shaped loading hopper. The loading hopper I0 is supported on the top of the stack 2 by means of a frame I I. The loading hopper l0 terminates at its lower end in a rectangular spout I2, which is made smaller than the mouth of the roasting chamber 3, into which it extends to provide a clearance space through which waste gases may be floated ofi.

As the temperatures at this part of this oven are not extreme, I make the loading hopper l out of metal of high thermal conductivity values.

The apron HI of the loading hopper It may be provided with ports Hl opening upward and outward so as to allow escape of waste gases from the raw material as it is being dried and heated.

The furnace structure proper of the stack consists in the rectangular brick work of the stack 2 from its floor up to line x--.r, and is designated by numeral l3. Through holes I4 in the opposite narrow walls of the furnace I3, are mounted burners 15. These burners are mounted, preferably, in such a position thatthe flames coming from them strike the roasting chamber 3 at right angles on its broad faces. While most of the combustion takes place in the furnace l3, it is true that, under some conditions, some of the combustion takes place at points higher up in the stack 2. To insure complete combustion, adjustable dampers l6 (see Fig. are provided in the floor of the furnace l3 to admit excess air when needed. It has been found advantageous to carry the burner feed lines l1, both fuel and air, through the furnace so that both the air and fuel may be preheated for the sake of economy and for the sake of producing higher burning temperatures in the burner flames.

Referring to Figs. 5 and 1, numeral I 8 designates a take-off hopper and 19 a metering valve mounted at the extreme lower end of the take-off hopper to enclose the same. The metering valve I9 is of a cylindrical shape and is provided with longitudinal pockets 20.

When the metering valve I9 is rotated, the measures of stone that settle into the pockets are passed out and allowed to fall by gravity into some suitable container or onto a moving conveyor.

The stack 2 is provided with suitable peep holes 2|, through which the temperatures of the products of combustion may be observed at the various points of its travel.

This oven may be constructed in various sizes,

depending on the volume or materials to be treated, or may be constructed in a battery of units. It has been found practical that an oven of .this type to ft. in height will provide sufiicient contact surface for the preheating and the separation of gases, complete burning of the raw material, and also provide a preliminary cooling chamber in the oven. The burner should be placed at about one-fourth the height of the oven, the ports at about two-thirds to threefourths of the height of the oven.

Among the ores and minerals that can be burned, roasted, vitrified, disintegrated, reduced or fused in the oven, are: galena, sphalerite, chalcopyrite, chalcocite, pyrites, gypsum, cerrusite, smithsonite, limestone, marble, malachite, azurite, magnesite, dolomite. The principal byproduct gases given off by the above named materials are sulphur dioxide (SOz),'having a specific gravity of approximately 2.2, and carbon dioxide (CO2), having a specific gravity of approximately 1.5 as compared with air. The ore or mineral to be treated is first crushed to a size that will permit it to be readily attacked by heat. Generally, a fineness that will pass a one or two inch screen is sufficient.

If the ore or mineral to be treated istobe acted on with a reagent, oxide or silicate, this oxide or silicate or other agent is then mixed with the stone charge either before or after crushing. r

In operating my oven, the roasting chamber 3 is supplied with stone or the like from the hopper H]. The roasting chamber 3 should be kept filled and an extra supply of the stone or the like should be held in the hopper.

As the flue gases issuing from the stack 2 must, by design, impinge on the hopper, the portion of the charge in the hopper is heated by the transfer of the heat from the flue gases to the charge through the metal hopper. The hopper is made out of an efficient heat conducting'metal, whereby, to more effectively use the waste heat of the escaping flue gases.

The valve 20 at the bottom of the take-off;

hopper acts as a closure for it. Through the means of pockets 20 in the surface of the valve, definite quantities of the burned charge may be metered out as the, valve is revolved. In this way the entire chargein the roasting oven is gently lowered. As the roasting oven 3 is vertical, the force of friction of the roasting ovens walls on the charge will be too slight to stir up the charge, with the consequence that the entire charge in the roasting chamber 3 may be lowered as a unit.

The heat necessary to reduce the charge to oxides and the by-product gases, S02, CO2, etc., is supplied by burning fuel through means of burners I5. Gas or oil are excellent fuels to use in this oven because the combustion of these against the opposite broad faces of the roasting '35 chamber 3. This is the hottest point in the oven. The fuel and air supplies, as previously explained, are preheated to effect a higher temperature than would ordinarily occur from the burning of a mixture of cold fuel and air, since the heat 1 requisite to bring themixture up to the flash point has been already partly supplied to the fuel and air themselves separately.

To insure complete combustion, excess air'is admitted through the floor of the furnace to the 1 stack 2 by means of dampers I6. An occasional baffle member 2 may be extended inwardly from the stacks inner Wall into the flue tocreate eddies and prevent the flue gas from channelling and passing out without giving up its heat.

The temperature in the furnace portion l3 of the stack 2' and the other portions of the stack and the resulting temperature in the roasting chamber 3 itself will depend on' the material being treated and the length of time such material remains in the oven. 7

For example, the temperature range necessary to reduce normal carbonates inside the roasting chamber 3 proper would have to be'from 1200 F. to 3000 F. to produce metallic oxides and C02.

The temperature of the flue gases leaving the stack should be maintained at about 200 'F'.

At no place in the stack 2 are the products of combustion allowed to come in direct contact with the charge itself. All of the heat that the charge in the roasting oven 3 receives from the combustion of the fuel has to pass through the walls of the roasting chamber 3. This feature of our invention is very important since it insures againstany contamination of the charge from the fuel. 7

From the drying zone A, where the charge is dried in the hopper by the es caping flue gases, the charge passes into a preheating zone B at the top of the roasting chamber. In-zone'B 18.3575

charge is being heated both by the heat from the flue gases and also by ascending gases which have been generated lower down in the roasting oven 3. In the preheating zone B, exhaust ports 6 provide communication between the roasting oven 3 and the discharge manifolds 5, provided with discharge pipes 1, whereby the gases generated in the roasting oven 3 may be drawn ofi.

In the generation of S02 or CO2, which have greater specific gravities than air moisture and the other gas impurities, the flow from the exhaust pipes may be so restricted as to build up the level of the column of S02 or CO2 with a resulting increase in pressure to such an extent that the gas impurities, and even a part of the $02 or CO2 may be floated up and out of the roasting chamber 3. Since the CO2 gas which is generated at the bottom portion of the vertical retort is heavier than the air and moisture in the portion of the charge at the top portion of the retort the volume of CO2 gas and volume of air and moisture will remain separated along a natural level in the absence of any stirring action. To assure that there will be no stirring action during the carrying out of this process the charge of ore that is being heated is lowered as an undisturbed unit. That is to say the individual lumps of ore in the charge stay in their same relative position with respect to one another during their entire travel through the oven. This type of operation of our oven will insure the production of a very pure gas. As the charge is lowered past the exhaust ports 5, any generated gas which was trapped in the voids of the charge may be drawn off along with the ascending stream of generated gas.

After the charge has passed down through the preheating zone B, it enters into the reducing zone C in the oven, where the charge in the roasting chamber 3 is burned, fused, vitrified or otherwise reduced.

When a charge of normal carbonates is used, it will be completely reduced in this zone to its metallic oxides and. CO2.

In leaving the reducing zone C, the charge passes through the cooling zone D, preparatory to entering the take-off hopper l8. In cooling, the charge gives up part of its heat to the incoming fuel and air being brought to the burners.

From the cooling zone D the charge, now the finished product, enters the take-01f hopper I8, which, as previously explained, is closed at its bottom by a metering valve l9.

The metering valve 19 is intended to be rotated by a gear or like means and its speed to be controlled by a suitable control means so that the down flow of the charge may be uniformly controlled.

When the temperature of the burners is held constant, the entire regulation of the furnace resolves upon the regulation of time under which the charge is subject to the constant temperature. The time element is determined by the rate of flow of the charge which is in turn regulated by the metering valve [9. And so I say that, with a constant temperature maintained, the degree to which the charge is burned may be controlled by regulating the meter valve l9.

To insure the purity of the by-product gases, care must be taken when drawing off the byproduct gases to maintain sufiicient pressure in the preheating zone B at the ports 5, so that no down draft is created in or through the top portion of preheating zone B above ports 5 and to maintain a proper separation zone between the generated by-product gas and the gas impurities.

It is to be understood that the form of my invention shown and described is to be taken as only a preferred embodiment of the same, and that various changes in size, shape and arrangement of parts may be resorted to without departing from the spirit of my invention or the scope of the subjoined claim.

Having thus described my invention, I claim:

The method of treating carbonates, comprising applying heated products of combustion to the exterior of a vertical retort having its upper end open and in free communication with the atmosphere so that the heat applied to the retort decreases upwardly for afiording a lower reducing zone and an intermediate pre-heating zone and an upper drying zone, introducing a loose charge of a carbonate comprising aggregates which are approximately one-inch to twoinches in size and having voids between them into the upper open end of the retort and gradually moving the charge downwardly through the retort so that it is subjected in succession to the action of heat in the drying and pre-heating and reducing zones, discharging the gases from the charge in the drying zone upwardly through the open end of the retort, preventing any substantial amount of gases other than carbon dioxide gas from entering the pre-heating zone by causing a portion of the carbon dioxide present in the pre-heating zone to pass upwardly through the voids in the charge in the preheating zone and drying zone and thereby forcing other gases through the voids in the drying zone and finally discharging to the atmosphere through the upper open end of the retort, and withdrawing a portion of the carbon dioxide from the pre-heating zone.

PARKER McCOMB.